The present invention is related in general to an assembly for mounting a wheel to a wheelchair frame. More particularly, the invention relates to a wheelchair drive wheel mounting assembly that permits adjustment of the camber angle of the drive wheel.
It is known to enhance the stability and control of a wheelchair by adjusting the camber of the wheelchair drive wheels. The camber of the drive wheels may be adjusted so that the drive wheels rotate in a plane that is angled relative to a vertical plane. Consequently, the axis of rotation is angled relative to a horizontal axis. The camber is typically adjusted so the top of the drive wheels are spaced closer together than the bottom of the drive wheels. The angle of the axis of rotation relative to the horizontal axis is commonly referred to as the "camber angle." Camber angles often range from about zero to about sixteen degrees. The amount of camber angle is often dependent upon the space and activity in which the wheelchair is being operated. For example, narrow paths of operation, such as hallways or corridors, may dictate that the camber angle be sufficiently small enough to fit within the path of operation. Conversely, activities that require a great amount stability and control may necessitate a relatively large camber angle.
Devices for permitting the adjustment of the camber angle of drive wheels are known. For example, it is known to provide an axle tube that is adapted to receive a camber tube which, in turn, is adapted to receive camber plugs. Counterbores extend through opposing ends of each plug. Each counterbore is disposed at a predetermined angle and position. Each counterbore defines a recess for receiving a drive wheel axis. The camber angle of each drive wheel may be changed by removing the camber plug from the camber tube, turning the camber tube 180 degrees, and reinserting the camber to tube into the axle tube. An example of this arrangement is shown in U.S. Pat. No. 5,851,018, issued to Curran et al. Other camber plugs are shown in U.S. Pat. Nos. 5,131,672 and 5,320,373, both issued to Robertson et al. Robertson et al. disclose various camber plugs each having a different camber angle. The camber plugs are releasably attachable within a recess in the sides of the wheelchair chassis.
Conventional camber angle adjustment devices have a disadvantage in that they require the timely and often cumbersome task of removing a camber plug from a tube, turning the plug in some way, and then reinserting the plug into the tube. A wheel mounting assembly is needed that permits adjustment of the camber angle of the drive wheels without having to remove or rotate a camber plug.